External wall insulation
Government planning regulations allow external wall insulation on domestic properties without the need for planning permission, but only if there is no material change to the external appearance of the property.
External insulation involves adding a decorative weather-proof insulating treatment to the outside of your wall. The thickness of the insulation needs to be between 50mm and 100mm. External wall insulation may therefore be permitted development however, there are important limits and conditions to permitted development rights, which must be met to benefit from these rights. For information on permitted development rights, visit the interactive guidance on the Planning Portal website.
If you believe your proposed works would be lawful under the permitted development regulations, and you require written confirmation from the council that your proposed external wall installation does not need planning permission, you are advised to submit an application for a lawful development certificate.
If your installation will materially change the external appearance of the building, you will need to apply for planning permission.
In order to protect the established character of our homes, council policy and guidance discourages the use of external insulation where it would harm the appearance of the building. For that reason, internal wall insulation is often preferable on street facing elevations with external wall insulation used on less visible parts of the building.
Further guidance on external wall insulation can be found in the Lambeth Design Guide - Building Alterations, Extensions and Retrofit (PDF 2.7MB)